Water is the most important chemical compound on the planet: 70% of the Earth's surface corresponds to the seas and oceans. The human body contains 65% of its weight as water and the Earth's atmosphere contains 0.001% water. In the human body, the blood contains 85%, the intestinal juice 99.3%, the gastric juices 99.4% and saliva 99.5% water, hence the importance of water in biological processes. An essential component of life on Earth, water is the preeminent solvent in industrial and biological chemistry. It should be pointed out that if in industry the purity of the water is essential, it is even more so in biology. Despite all research, the water molecule remains strange and poorly understood. There are in fact several types of water molecule, which means that water is a mixture of chemical compounds. The predominant molecule is H2O, but because of the isotopes of hydrogen and oxygen, there are correspondingly 18 kinds of water molecule. More particularly, there are small quantities of heavy water or D2O, which is a neutron moderator, whereas H2O is a neutron capture agent. Tritiated water, T2O, which is radioactive, is found in rainwater in very small quantities. With D2O biological reaction rates are lower and the physical constants are slightly different (the density of D2O is greater than 1).
In the Periodic Table of the Elements, oxygen is element No. 8 and is found on the second row of column VI. Corresponding to each element of the family in column VI is a hydrogenated compound:
O (oxygen)H2OS (sulfur)H2SSe (selenium)H2SeTe (tellurin)H2Te
In general, the physical and chemical properties of the elements of any one column are similar or change in a regular fashion. In the case of water, certain constants are unexpected: high values are found for the melting point, the boiling point, the latent heat of vaporization (Hv), the heat of melting (Hm) and the specific heat (Cm), and water has a maximum density at C and a high dielectric constant (∈r). These anomalies stem from the existence of particular bonds between water molecules in the solid state, in the liquid state and even the gaseous state (the number of anomalies is 38).
More particularly, the melting point and boiling point are abnormal for water compared with the family of hydrogenated compounds of the elements of the family in column VI.
H2SH2SeH2TeH2OTm−51° C.  −60° C.−85.6° C.   0° C.Instead of −100° C.Tb −2° C.−41.5° C.−60.7° C.+100° C.Instead of −80° C.
Moreover, in the case of the other liquids the density decreases linearly as the temperature increases, which is not true for water, except for at high temperature. The maximum density is observed at 4° C. at 1 atmosphere, here again because of its peculiar structure.
According to Dr. Lorenzen, an expert in biology, the water contained in sugared beverages, beer, etc. is not, or little, used by cells and is expelled directly via the kidneys.
Depending on the intracellular or extracellular medium, water adopts different configurations.
Each type of cell uses four principal types of configuration of water for its operation.
Water molecules grouped together in clusters or microclusters allow information transfer between cells: proteins of the information system are surrounded by nine rings consisting of microclusters. Therefore information can flow only if the water has a very particular structure—this structure is modified by temperature and the solutes that it contains.
It seems that the trimer (H2O)3 plays a predominant role in cell metabolism.
Water allows both assimilation during cell metabolism and waste transport, hence the need for pure water with a very low mineral content in order not to overload the electrolyte environment of the cell and modify the osmotic pressure therein.
In blood serum there are 80 g of proteins per liter and the viscosity is increased by a factor of two, while the presence of NaCl in the physiological saline does not modify this viscosity. Likewise, increasing the number of red blood cells in the blood increases its viscosity.
It therefore seems necessary that supply water be of the lowest possible mineral content so that it can fully play its bonded liquid role in exchanges with the cell.
The benefit of water with a low mineral content is that it can be much better assimilated by the cell and avoids overworking the kidneys to remove the minerals. This is because plants pre-assimilate the trace elements that the organism is incapable of assimilating directly (man and animals are heterotrophic, while plants are autotrophic).
Professor Schroder, a world authority on the subject of water, contests the recommendation for mineral-laden water for supply.
Moreover, although perfectly pure water has a pH of 7 at 25° C. and is very sensitive to external attack by acids or bases, mineral-laden water that contains hydrogenocarbonate ions is less sensitive, owing to a buffer effect.
The presence of calcium ions (Ca2+) and magnesium ions (Mg2+) gives the water a certain hardness characterized by its total hardness (TH). In the case of water for beverages, legislation imposes a total hardness such that: 15<TH>25, whereas perfectly assimilable water must have a total hardness TH.
From the same source, to use softeners is not recommended since replacing calcium and magnesium ions with sodium ions is not beneficial to health.
Water that contains silica and has also been demineralized may have a slightly acid pH.
Water and extracellular and intracellular exchanges:
In order for cell life to be maintained, many diverse substances must continually cross the plasma membrane. Sugars, amino acids and other nutrients must enter the cell so as to meet its energy requirements and sustain its growth; waste and other degradation products must be removed therefrom, as they are toxic for the cell. Ions must be transported in both directions, so as to maintain the ionic composition of the intracellular medium, which is very different from the surrounding medium—it is much richer in potassium ions and less rich in sodium ions. These inequalities lead to leaks (due to osmotic principles) which must be compensated for by transport, in the reverse direction, against the concentration gradient. All this entails intense two-way traffic across the plasma membrane (a continuous phospholipid double layer) involving diffusion phenomena (simple or facilitated diffusion) and active transport. Only water is capable of allowing this transport.
These notions show that the plasma membrane is an important structure for maintaining the concentrations of ions and molecules in the cell and for its biochemical isolation with respect to the outside or to other cells.
These exchanges across the cell membrane show the importance of water.